Power transmission belt and method

ABSTRACT

The invention comprises a belt having a plied construction overlying tensile cords. An elastomeric layer overlies an overcord which overlies yet another elastomeric layer which in turn overlies a tensile cord. The overcord layer supports the tensile cords during molding thereby stabilizing a cordline centerline position with respect to a rib apex. This construction significantly reduces a distance from a tensile cord centerline to a rib apex and rib/pulley interface in a multi-ribbed belt, thereby significantly increasing belt life.

FIELD OF THE INVENTION

[0001] The invention relates to power transmission belts having a lowcordline and a method of producing same.

BACKGROUND OF THE INVENTION

[0002] It is known in the art to make power transmission belts fromelastomeric materials having an embedded tensile member. The belts maydescribe a multi-rib, toothed or v type profile. The belts run inpulleys having a cooperating profile.

[0003] It is known that the tensile cord in power transmission belts isgenerally disposed in an elastomeric matrix. In particular, onmulti-ribbed belts the tensile members are disposed in the body of thebelt. This form of construction places an increased lever arm on thebelt rib which is supported by the tensile members. The amount of forceexerted is in direct proportion to the radial distance from the centerof the tensile cord line to the bearing surface of the mating pulley. Alonger lever arm length diminishes the operating life of the belt.

[0004] The method of fabrication of the belt determines, in part, thelocation of the tensile cord. In the case of ground belts, a belt slabis molded and vulcanized on a mandrel. The belt slab is then removed andthe multi-rib profile is then ground into the belt slab. Since thegrinding operation cannot be completely controlled, some allowance mustbe made in the location of the tensile cord to prevent it from being cutby the grinding operation. This results in the tensile cord line being alarger than preferred distance from a rib apex.

[0005] Representative of the art is U.S. Pat. No. 3,820,409 to Meadowswhich discloses a v-belt having a plurality of closely spaced supportingcords arranged transverse to and on at least one side of the loadcarrying cord.

[0006] What is needed is a belt having a significantly reduced distancefrom a tensile cord to a rib apex. What is needed is a belt having asignificantly reduced distance from a tensile cord to a rib/pulleyinterface. What is needed is a belt having an overcord layer disposed inan elastomeric layer overlying a tensile cord for controlling a tensilecord location during molding. The present invention meets these needs.

SUMMARY OF THE INVENTION

[0007] The primary aspect of the invention is to provide a powertransmission belt having a significantly reduced distance from tensilecord to a rib apex.

[0008] Another aspect of the invention is to provide a powertransmission belt having a significantly reduced distance from a tensilecord to a rib/pulley interface.

[0009] Another aspect of the invention is to provide a powertransmission belt having an overcord layer disposed in an elastomericlayer overlying a tensile cord for controlling a tensile cord locationduring molding.

[0010] Other aspects of the invention will be pointed out or madeobvious by the following description of the invention and theaccompanying drawings.

[0011] The invention comprises a belt having a plied constructionoverlying tensile cords. An elastomeric layer overlies an overcord whichoverlies yet another elastomeric layer which in turn overlies a tensilecord. The overcord layer supports the tensile cords during moldingthereby stabilizing a cordline position. This construction results in asignificantly reduced distance from a tensile cord centerline to a ribapex and rib/pulley interface in a multi-ribbed belt.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a cross-sectional view of the prior art.

[0013]FIG. 2 is a cross-sectional view of the inventive belt.

[0014]FIG. 2A is a detail of FIG. 2 after the molding operation.

[0015]FIG. 3 is a chart of test results for the inventive belt.

[0016]FIG. 4 depicts high load life test results for the inventive belt.

[0017]FIG. 5 depicts a high temperature durability life for theinventive belt.

[0018]FIG. 6 is a cross-sectional view of a -d dimension.

[0019]FIG. 7 is a side view of a belt section.

[0020]FIG. 8 depicts conventional overcord construction.

[0021]FIG. 9 depicts overcord construction for the inventive belt.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022]FIG. 1 is a cross-sectional view of the prior art. The prior artconstruction comprises an overcord A, undercord B and tensile cords C.The cord line is shown at a given distance d from an apex of amulti-ribbed profile. The cordline must be at a sufficient distance dfrom the rib apex to avoid being damaged when the multi-rib profile isground into the belt.

[0023]FIG. 2 is a cross-sectional view of the inventive belt. Belt 100comprises a plurality of layers. Undercord 14 comprises a multi-ribbedprofile in the preferred embodiment. In operation, belt 100 engagespulley P.

[0024] More particularly, layer 10 comprises gum or fiber-loadedelastomeric material. Overcord or cross-cord 11 comprises a cross-cordlayer. The cross-cord layer supports tensile cord 13 during the moldingand curing process, maintaining a proper cordline location within thebelt body. Cross-cord 11 may comprise woven or non-woven material.

[0025] Cross-cord layer 11 is substantially non-porous, preventing asignificant amount of layer 10 from penetrating through layer 11 duringthe molding process. This has the effect of layer 11 supporting tensilecord 13 thereby controlling a tensile cord centerline CL location.

[0026] A thin layer of gum 12 is applied between layer 11 and thetensile cord 13. Cords 13 extend along a longitudinal axis of the belt.Although in the preferred embodiment the gum 12 layer is applied betweenlayer 11 and tensile cords 13, gum 12 may also be applied betweentensile cords 13 and undercord layer 14 so long as cords 13 areencapsulated by gum 12 during molding. Undercord 14 comprises anelastomeric material having a fiber loading. In an alternate embodimentit may also comprise pure elastomeric without fiber loading. The fiberloading for layer 10 and 14 may be in the range of 0.1 to 20 parts perhundred. The fibers may comprise any known in the art, including by wayof example cotton, PTFE, and aramid.

[0027] Jacket 15 may comprise woven or non-woven material in order toestablish a coefficient of friction.

[0028] Manufacturing.

[0029] The inventive belt is constructed in a process of sequentialapplication of each layer on a build drum. The belt is fabricated bymolding using an expanding membrane that presses the belt slab into aribbed outer shell. In this process the belt is built-up on a mandrelhaving an expandable member on the surface of the mandrel. Duringmolding and curing the expandable member presses the belt build into anouter shell mold. Use of the cross-cord overcord ply 11 stabilizes thetensile cordline 13 position, resulting in a precisely controlledcordline position. This allows the tensile cord 13 to be placed closerto a rib apex 16, and thereby closer to a rib/pulley interface RPsignificantly increasing operating life. By comparison, prior artcordlines are at a greater distance from a rib apex and rib/pulleyinterface, resulting in a shorter operational life.

[0030] In particular, a first elastomeric layer 10 of a gum elastomericor fiber-loaded material is plied on the mandrel. Next, a cross-cordlayer 11 is applied. Due to the flow characteristics of the gum duringmolding, the cross-cord layer 11 can be butt-spliced by stitching theends of the ply together or left with a gap as described in FIG. 9.

[0031] Next, a second elastomeric layer comprising a thin ply of gumstock 12 is applied over the cross-cord ply 11. Layer 12 is solely madeof rubber stock in the preferred embodiment. Next, the tensile membersor cords 13 are wound over the gum stock ply. Next, the thirdelastomeric layer comprising a fiber-loaded undercord ply 14 is applied.Finally, a ply of non-woven material 15 is applied to the surface of theundercord ply. Non-woven material 15 may comprise cellulose ornon-cellulose based materials.

[0032] Use of the build and process results in the final cord positionremaining stable and significantly closer to a rib apex 16 andrib/pulley interface RP. In particular, during the inverted moldingoperation the belt build, and cord 13 in particular, is spiraled onto anexpanding membrane positioned in a build drum. During molding theexpanding membrane or bag pushes the belt build into the mold shellribs.

[0033] In the prior art during a forming sequence the cord 13 tended toeither distort or pull down into the first available support layer. Theresulting misalignment of the cords caused them to have differing loads,thereby decreasing the operational life.

[0034] In the inventive belt and process, the support to prevent thisoccurrence is provided by cross-cord layer 11. In this manner the cord13 is supported causing cordline CL to be placed more precisely andcloser to the rib/pulley interface RP.

[0035] This construction also has a significant advantage over thefabrication method wherein a belt profile is ground into the cured beltbuild. In the case of a ground belt the cord line must be located agreater distance from a rib apex 16 to avoid having the cordinadvertently damaged by the grinding operation. In the instant moldedconstruction, the cord line is much closer to the apex.

[0036] The disclosed construction of the inventive belt places cordlineCL at a lesser radial distance d above an rib apex 16 and rib/pulleyinterface RP (d2) as compared to prior art belts. Positioning thecordline in this manner provides superior dynamic performance, see FIG.3. The range of radial distance d in the inventive belt is such that anouter surface of the cord 13 is approximately 0.000″ to 0.050″ above therib apex 16. It is also possible for the cordline distance d to benegative such that an outer surface of the cord is below the rib apex,effectively placing cord 13 partially or totally within the ribs, seeFIG. 6. The distance of a cord centerline relative the rib apex is inthe approximate range of −0.040″ to 0.000″. The negative value, forexample, −0.040″, indicates the cord is “below” the rib apex such thatthe cord is set within the ribs, see FIG. 6, a cross-sectional view of a-d dimension.

[0037] In the preferred embodiment the range of d is approximatelybetween 0.010″ and 0.015″ above the rib apex for a cord 13 having adiameter of approximately 0.040″. In the case where radial distance d isequal to 0.020″, a tensile cord 13 is at the surface of layer 14 at arib apex 16. The cord diameter given herein is for illustrative purposesonly and may be varied depending upon the needs of a user and operatingconditions of the belt.

[0038] As previously noted, the disclosed construction of the inventivebelt has the effect of reducing a distance d2 from a rib/pulleyinterface RP to the belt cordline CL. Reduction of distance d2 causes areduction of the magnitude of the deflection of the rib as the beltengages a pulley. More particularly, during operation as a belt engagesa pulley the rib elastomeric material deflects in response to the torquebeing transmitted to the pulley. The deflection is along a longitudinalaxis and is relative to a point on the tensile cord. See FIG. 7.

[0039]FIG. 7 is a side view of a belt section. A represents a point on atensile cord 13. C represents a point on a pulley engaging surface of arib 14. When the belt under load L engages a pulley (not shown), rib 14deflects such that point C moves to point B through a distance D3. Themagnitude of distance D3 is a function of d2 as described herein. As d2is increased, so is D3. Conversely, as d2 is decreased, D3 is decreased.Excessive deflection, D3, causes premature belt failure by rib cracking.Reduction of deflection D3 during operation by significantly reducing d2significantly increases the life span of the inventive belt.

[0040]FIG. 2A is a detail of FIG. 2 after the molding operation. Afterthe manufacturing process is completed, the belt cross-section is suchthat elastomeric layer 12 has been pressed between and through thetensile cords 13 forming lobes 120. Lobes 120 run along a length of thetensile cords, substantially parallel to a longitudinal axis. Fabriclayer 11 is also pressed among the tensile cords and bears upon a thinremaining portion of layer 12 upon cords 13. Lobes 120 compriseelastomeric from layer 12. Lobes 120 are disposed between the cords 13and a rib apex 16. The lobes provide support for the cords duringoperation.

[0041]FIG. 3 is a chart of test results for the inventive belt. As shownin FIG. 3, reducing the average distance between a rib apex 16, andthereby rib/pulley interface RP, and the cordline CL significantlyincreases belt life. For example, belt life for a belt having an averagetensile cord centerline to rib apex radial distance d of approximately0.022″ is 100 hours as compared to 280 hours for a belt having anaverage tensile cord centerline to rib apex radial distance d ofapproximately 0.012″.

[0042]FIG. 4 depicts high load life test results for the inventive belt.The inventive belt exhibited significantly improved high load life. Thehigh load test comprises running a belt at approximately 4900 RPM underapproximately 264 pounds total tension at a temperature of approximately85°. The inventive belt operated approximately 280 hours to failurewhile a belt having a higher cordline location operated less than 150hours to failure, an improvement of 86%.

[0043]FIG. 5 depicts a high temperature durability life for theinventive belt. The inventive belt exhibits significantly improved hightemperature durability. The high temperature durability test comprises arunning a belt on a three point drive at approximately 13000 RPM underapproximately 282 pounds total tension at a temperature of approximately250° F. The inventive belt operated approximately 390 hours to failurewhile a belt having a standard cordline operated 250 hours to failure,an improvement of 56%.

[0044]FIG. 8 depicts conventional overcord construction. Overcord layerC is joined at a lap joint. An end of the lap joint overlays the lowerportion by an amount OL. This “high spot” creates a bump that can causenoise during operation in the case of use of the belt with a backsideidler.

[0045]FIG. 9 depicts overcord construction for the inventive belt. Asdescribed elsewhere in this specification, layer 10 overlays cross-cordlayer 11. D depicts the build drum upon which the belt is layed-upduring fabrication as described elsewhere in this specification. Ends11A and 11B of layer 11 may be configured in a butt splice and/orstitched to each other. However, in the preferred embodiment, duringfabrication on the build drum a slight gap G may be present between theends 11A and 11B, allowing an end 11A to be stitched into layer 10instead of to the opposite end 11B. During vulcanization, the materialof layer 10 then flows together across the gap creating a seamlessjoint. A seamless joint eliminates any noise that might be caused by thebelt traveling over a backside idler. Consequently, fabricating the beltwith a gap on the overcord is an improvement over a prior art belt wherea gap on the overcord layer would cause noise in the case of use of abackside idler because the prior art belts require the ends of theovercord layer to be closely controlled. The inventive belt does notrequire the ends of layer 11 to be precisely cut and layed-up alsoresulting in decreased fabrication costs.

[0046] Although a single form of the invention has been describedherein, it will be obvious to those skilled in the art that variationsmay be made in the construction and relation of parts without departingfrom the spirit and scope of the invention described herein.

I claim:
 1. A method of building a belt comprising the steps of:building a belt build comprising the steps of; plying a firstelastomeric layer on a build mandrel, the build mandrel having anexpandable outer surface; plying a cross-cord layer on the elastomericlayer; plying a second elastomeric layer on the cross-cord layer;spiraling a tensile member on the second elastomeric layer; and plying athird elastomeric layer on the tensile cord; pressurizing the expandableouter surface thereby pressing the belt build into a mold having a beltprofile; supporting the tensile member with the cross-cord layer wherebya tensile cord position is controlled; applying a temperature to thebelt build; curing the belt; and removing the belt build from the mold.2. The method as in claim 1 further comprising the step of plying anon-woven material on the third elastomeric layer.
 3. The method as inclaim 1 further comprising the step of using a multi-ribbed profilehaving rib apexes.
 4. The method as in claim 3 further comprising thestep of cutting the cured belt build into belts.
 5. The method as inclaim 1 further comprising the step of using a fiber loading in thefirst elastomeric layer.
 6. The method as in claim 1 further comprisingthe step of using a fiber-loading in the third elastomeric layer.
 7. Themethod as in claim 1 further comprising the step of limiting a distancefrom a rib apex to a tensile member centerline to a range of −0.040″ to0.015″.
 8. The method as in claim 9 further comprising the step offorming the second elastomeric solely of rubber.
 9. A belt comprising: afirst elastomeric layer; a first cross-cord layer bonded to the firstelastomeric layer; a tensile member extending along a longitudinal axisof the belt; a second elastomeric layer bonded to the cross-cord layerand overlaying the tensile members and extending between the tensilecords forming lobes disposed between the tensile cords and a rib apex,the lobes being substantially parallel to the tensile cords; and a thirdelastomeric layer bonded to the second elastomeric layer having aprofile.
 10. The belt as in claim 11 further comprising a fiber loadingin the first elastomeric layer.
 11. The belt as in claim 11 furthercomprising a fiber loading in the third elastomeric layer.
 12. The beltas in claim 11, wherein the second elastomeric layer is solely made ofrubber.
 13. The belt as in claim 11 further comprising a multi-ribbedprofile.
 14. A belt comprising: an elastomeric body having a rib apexdisposed in a longitudinal direction; a tensile member disposed in alongitudinal direction and disposed within the elastomeric body relativeto a rib apex, and having a radial distance d between a tensile membercenterline and the rib apex; a crosscord layer disposed adjacent thetensile member and opposite the rib apex.
 15. The belt as in claim 14further comprising a fiber loading layer bonded with the elastomericbody at a pulley interface.
 16. The belt as in claim 14, wherein theelastomeric body is solely made of rubber.
 17. The belt as in claim 14having a radial distance d in the range of approximately −0.040″ to0.050″
 18. The belt as in claim 14 having a radial distance d in therange of approximately 0.020″ to 0.015″.
 19. The belt as in claim 17,wherein the crosscord layer further comprises woven material.
 20. Thebelt as in claim 17, wherein the crosscord layer further comprisesnon-woven material.
 21. A belt comprising: an elastomeric body having arib apex disposed in a longitudinal direction; a tensile member disposedin a longitudinal direction and disposed within the elastomeric bodyrelative to a rib apex, and having a radial distance d between a tensilemember centerline and the rib apex in the range of approximately −0.040″to +0.050″.
 22. The belt as in claim 21 further comprising amulti-ribbed profile.
 23. The belt as in claim 21 further comprising acrosscord layer disposed adjacent the tensile member and opposite therib apex.
 24. A belt comprising: an elastomeric body having at least tworibs running longitudinally and having a rib apex disposed in alongitudinal direction; and a tensile member disposed in a longitudinaldirection and disposed within the ribs.
 25. The belt as in claim 24further comprising a radial distance d between a tensile membercenterline and the rib apex in the range of approximately −0.040″ to+0.020″.
 25. The method as in claim 1, further comprising the step of:forming a gap between ends of the first elastomeric layer.
 26. Themethod as in claim 1, further comprising the step of: forming abutt-splice between ends of the first elastomeric layer.